1. Field of the Invention
The present invention relates to an image forming apparatus using an intermediate transfer member, and an intermediate transfer member and image forming method to develop an electrostatic latent image formed on the surface of a latent image carrying member using a liquid developer containing toner particles dispersed in a fluid medium.
2. Description of the Related Art
Electrophotographic methods can be broadly divided into dry developing methods and wet developing methods. Among these methods, wet developing methods using liquid developer containing toner particles dispersed in a fluid medium have realized toner particle sizes in the submicron range and provide advantages of high image resolution, excellent halftone qualities and are easily fixed compared to dry developing methods.
In conventional wet developing methods using toner particles in the submicron range, an electrostatic adhesion force is strengthened between toner and the image carrying member such as a photosensitive member or the like due to the higher charge of the toner. Accordingly, not only is a high electric field is necessary for electrostatic transfer of the toner on the surface of an image carrying member to a recording member such as plain paper, overhead projection (OHP) sheets or the like, but transfer efficiency is extremely poor, and image disruptions during transfer readily occur. Thus, the recording member should have excellent transfer efficiency, for example, disadvantages occur relative to plain paper and OHP sheets when thinner than normal transfer sheets or coated sheets are required. Furthermore, when producing full color images, toner images for each color must be overlaid one upon another via three or four transfers, such that the previously mentioned disadvantages become even more pronounced.
A separate disadvantage of methods which directly transfer toner images maintained on an image carrying member to a transfer sheet such as plain paper and the like is that paper debris such as paper fibers and the like readily adhere to the image carrying member during transfer and reduce the function of developing device, cleaners and the like.
Image transfer methods using intermediate transfer members have been proposed in U.S. Pat. Nos. 5,089,856, 5,047,808, 4,999,677, 4,984,025, and 5,158,846 to improve the previously mentioned disadvantages.
In image transfer methods using the aforesaid intermediate transfer members, after a toner image is developed on the surface of an image carrying member, said toner image is temporarily transferred (primary transfer) to an intermediate transfer drum (or an intermediate transfer belt) disposed so as to make contact with said image carrying member and with an electric field effectively formed therebetween. Thereafter, the toner image is transferred (secondary transfer) to a recording sheet or the like via heat and/or pressure, or electrostatic force generated by an electric field, and the consecutive transfer operations are completed.
Thus, the transfer characteristics required to transfer a toner image from an image carrying member can be maintained by the intermediate transfer member by using the previously described intermediate transfer member, such that the freedom of recording member selectivity is greatly increased. As a result, recording members whose transfer characteristics are different each other such as plain paper, OHP sheet and the like can be used, and even full color images via toner image overlays are easily reproducible.
However, in image forming apparatus and the like using the previously described intermediate transfer members, transfer from an image carrying member (primary transfer) in combination with liquid developer technology is inadequate and produces image drift. Thus, transfer efficiency when transferring a toner image from said intermediate transfer member to a recording member (secondary transfer) is also inadequately accomplished.